1. Field of the Invention
The present invention relates generally to cellular mobile communication systems, and more specifically to a technique to prevent concentration of traffic in particular cell sites.
2. Description of the Related Art
In a known cellular mobile communication system, a mobile station is constantly making a search through the control channels of surrounding cell sites during a standby mode and tuning its frequency synthesizer to the control channel of highest field intensity. The cell site that uses that control channel is the home cell site for the mobile station. When placing a call, the mobile station sends a call request on the presently turned control channel to the home cell site to cause it to search through its channel resource for an idle speech channel. If the home cell site fails to locate an idle speech channel, it proceeds to make a search through the channel resource of an adjacent cell site. However, traffic concentration tends to occur in a particular cell site if the channel search is made without taking into account the usage of speech channels of the adjacent cell site. If the system covers an area where cells of smaller size are bordering on or partially overlapping cells of larger size, severe traffic concentration might occur in one or more greater cells due to the possibly large number of mobile stations in the greater cells in comparison with those in smaller cells. To meet such traffic demand, additional frequency resource must be allocated to the greater cells. Because of the high transmission power, the additional resource allocation results in an inefficient frequency reuse plan and a loss of frequencies which could otherwise be reused for remote cell sites.